It's probably just dust in the cooler's ribs.
Remove the bottom plate (see below), take one of those dust blower air cans, and blow it out.
Whith high probability the job is done.
Thermal paste is a critical beast. You need to disassemble the cooler from the CPU, which is within a laptop not as simple as within a desktop or tower PC. And afterwards re-assemble everything again correctly, which can be tricky with a laptop. Clean the old paste pretty well (don't mix up different pastes.) And be carful where you smear it. Those pastes are not really healthy.
Also there is lots of "voodoo" about thermal paste (compound actually), which you cannot wipe out with facts. Lots of this stuff is advertised with completely bogus values for thermal resistance. Arctic's MX-4 is in middle price range and the best thermal compound I know so far. They don't give you a value for the thermal resistance of their product (anymore), because if they'd give the true real value (which is pretty good) they cannot compete with all those made up bogus fantasy values of competitor's way more expensive "wonder" pastes. Tip: touch two different pastes (Don't smear it on your skin!) The one feels cooler has the better value, no matter what the producer tells or writes about his magic wonder stuff. Additionally almost all people I've seen so far, even real hardware pros in YT videos, all use
way too much paste ("The more the better." Wrong!) The paste shall only close the few, very small air gaps, but not separate the cooler from the CPU swimming on a film of paste. No paste - no matter how fantastic its wonder values are - is better than the direct contact bare metal to bare metal.
But, as I said, I suspect just dust.
P.S.
I never open laptop because this one is my first one and I do not want to make some damage.
I had opened several of those. You need the right tools:
fitting, not total low quality screw drivers, and also a plektrum can be of good use. Most important tools are sensitivity, carefulness and patience - never ever use brute force! If it can not unfixed without any force, you still have not found a screw or hook that needs to be unfastend first (There is always at least one screw below a sticker or another kind of seal you need to break [guarantee loss.])
If you don't have the total exotic special thing it's almost certain you will find detailed instructions for opening, disassembling, and resassembling on the net, mostly YT.
Search for and watch such first: You'll see: If you have the right tools, be careful, and not completely un-handy, it's no biggy.
At least to open the bottom cover to exchange storage drive, RAM or WLAN modules, or blow out dust. Remove cooler or the mainboard is a complete other beast.
Also: Avoid to touch directly on the electronics boards. For just cleaning it, you don't need to touch any electronics at all. And when exchanging modules, only touch the edges. There is a danger of high voltage electrostatics discharge from your body, which can destroy electronic parts.
If you do such things better have some
anti-static grounding wrist strap you can get for a few bucks.
But again:
First just clean it from dust, before you even think of thermal paste. For that you don't need to disassemble much. With most devices you just need to remove the bottom's enclosure plate.
But if you don't feel safe about it, check some smart phone repair shop; for those guys a laptop is kindergarden, and I guess they will open and clean it for you within 15 minutes for a small fee.
(haven't seen any paste that did anything notably different with temps though; even Kryonaut)
