I have a fully built pc not just fans. I was wondering if like smoke particles could have gotten under the cpu heatsink and into the motherboard or something to that effect
No. They could not. You are worrying about something that isn't even a thing. I even have systems running in my shop, where there is constantly smoke from grinding and cutting on metal, on wood, soldering smoke, fumes from a propane heater during the winter, various "smells" from the use of dozens of different chemicals, exhaust from vehicles, fumes from heating metal parts with MAP gas to get them loose enough to take apart and just occasionally, an actual fire. Others run computer systems in a variety of industrial applications where everything you can imagine could be in the air and dozens and dozens of computer systems are in use to run various machines, devices, make calculations, control anything you could think of that is used to manufacturer anything, and in none of these situations does anything "in the air" (So long as it's not something seriously caustic or corrosive, in which case if it was you'd be a fool to not have yourself and everything else safeguarded by expensive protective gear and have ample active ventilation in place) have any effect on those (Or my) systems.
Now, if you lit a pile of oil, or tires, or something like that on fire that was making a very specific type of greasy smoke, and your machine was sucking it directly in, it could POSSIBLY, EVENTUALLY, AFTER A LONG TIME, leave some sort of damaging film on things inside that the smoke came in contact with, but that would require an incredibly significant amount of smoke and it would need to be breathing it for a pretty extended period of time, like over days and weeks, to even likely have a measurable effect.
In your scenario, it isn't even possible much less feasible, that anything might happen as a result of there being some electrical stink in the air from overheating a power tool. It doesn't even bear consideration to be honest.