I do not think it was a cat scratch. It usually does not present as a visible lump. Even if so, it should have gone away completely by now.
It is possible that it is an enlarged lymph node
. A FNAC or Fine Needle Aspiration Biopsy
and Cytology of the lump can ascertain the exact cause of this.
It is done as an office procedure. Please discuss about this with your treating doctor.
I hope you get well soon.