My 19 month old just hit hit head really hard but is running around laughing and playing but there is a small bump should i get him checked out?

Yes: It's always a good idea to get toddlers checked out after head injury or fall. It may not be in emergency room but his doctor's office the same or next day.

No knockout/no pbm: The trauma that knocks you out, even briefly, has produced a concussion.If the trauma wasn't enough to cause even brief loss of function is minor. A bump coming out, means he has a blood pocket under the scalp, but should do fine.Some will throw up once or seem dazed with a headache.If he starts vomiting multiple times, i would have him seen.