Broken kitten leg help plz and agressive mom cat?

my frnd threw one of the kittens hard it hited a table and the bed and it wasnt able to move after takin it to the vet she gave him a needle and will give him another one tommorw she said its not broken but mayb somthing like inside bleedin the kitten aint walkin and the vet said i must give him wet food tuna or somthin but the mom cat is acting pretty agressive to him since he came back and makin that attacking sound he aint eatin or drinkin she became also agressive to the other kittens what can i do they r almost 2 months ;( help me plz