Bad behaviour

Hi ladies, my son is 3 he will be 4 in september his behaviour has changed dramatically. He is throwing things like when out a walk picking up stones and throwing them on road, destroying plants in garden he helped his dad plant tulips then tipped them all out, unwinding toilet roll took my lipstick drew all over bath. Hitting me during tantrums. He’s always been so sweet and loving but this is not him. Everything is an argument. Nursery said he’s fine in there just saying no. Only thing I’ve noticed is he keeps saying his cousin keeps hitting him and pushing him in nursery. There dads are cousins and do not speak. She hit him in December in nursery causing his nose to bleed and after a meeting it seemed to stop so not sure this is to do with behaviour. Any advice would be great.