Childs behaviour has changed. Is there something wrong with him?

My baby is 30 months old, started picking his words at 20months.

Smile and waves back at me and we even have a way of greeting each other like a sign.

All of a sudden he withdrew after I came back from 5weeks holiday and I thought it's was because had been away far too long, but I noticed he wasn't waving as usual and I realise the only words he could pronounce now are Daddy and mummy.

He's so aggressive and will not respond to his name.

I am worried as a father.

Could there be something wrong?