can not do pupu and has a ball in the anus I do not know if to push
It seems to be an infection of anal glands (sacs).
This infection is often reocurring, and mostly reserved for small breeds, even though large breeds can be affected too. Once infection happens, take your dog to a vet to drain the fluid out of anal glands.
When it happens more than three times in a row and in a short time, veterinarians often suggest to empty it surgically, to prevent it from happening again in the future, as it is a very annoying process for the dog.
However, it could be a different type of lump.
Lumps could be tumors or abscesses. Most abscesses get broken when they reach a certain size. If they continue to grow, there is possibility it could be a tumor.
To make sure what is it about, you should take your dog to see a veterinarian, in order to explore the lump and perform the appropriate tests.
All the best.