Fighting naps

Little one was such a good sleeper. Had mainly 3 naps daily and would fall asleep almost independently. Couple weeks ago he got a helmet and since then putting him to sleep was awful. Now he got used to the helmet but the last two days he has been fighting naps and bed time.. He is yawning and clearly tired but cried when I try to rock him and screams when I put him down. It’s not teething so not sure what it could be.. sleep regression I guess?