So I registered my motorcycle in MA early this year but left the country before I could get the safety inspection, and I won't be back until next year. Does the Mass gov check automatically to see if registered vehicles are inspected? Is there any sanction for registering vehicles but not getting them inspected? (I won't be riding it before re-registering it next year, I'll get the inspection after that)
Registering a vehicle for ownership and registering it for driving on the road are two different things.
If by "registered my motorcycle", you mean that you registered the ownership when you bought it, then it shouldn't matter.
Safety inspections (and liability insurance) are required when you register for a license plate, which allows the vehicle to be driven on public roads.