MacBook – Why is the MacBook getting hotter than usual since some time

Try resetting the SMC as noted in the question for your MacBook Air and see if the problem persists.

If the problem does persist it may be a failing temperature sensor, resulting in the fans running faster than normal to worst case fail-safe full-speed state, your only option at that point would be to take it to Apple Support for repair / replacement.

If you are confident with opening the case of your machine and blowing some canned air at it, this is said to take care of the dust accumulation that can cause overheating. Certainly no harm in it.