Those models with the P4 HT are well known to have issues with the heat sink mounting. The drop didn't help.

After you backup all your stuff and are ready, the common fix is to tear down the laptop to the motherboard then clean off the old heatsink paste, put on new and then build the machine up taking the usual care to see that every mount and connection is secure.

You don't want 3 out of 4 heatsink mount points but all 4.
Bob