Bump on one year olds head

I noticed a fairly large lump on the back of my one year olds head last night. He sometimes loses his balance and falls backwards and wacks his head on the hard wood floor. He doesn’t cry he just continues what he’s doing so I haven’t really thought much of it. Until I noticed this lump, he’s acting as usual but should I be concerned or call the doctor? He did throw up 3 times last night and he never does that.

But again, he’s acting fine and normal, not like he’s in pain or lethargic.