My cat June is 2 years old

Hello ! My cat June is 2 years old. She received her rabies vaccine on September 1. I did not notice any lump immediately after the vaccination. Recently, I noticed a small, hard, round lump on her back/shoulder area. It is more noticeable when she is sitting, but when she stands, it is not very prominent. It seems to stay in the same spot. She does not show any signs of pain or discomfort when I gently touch it. She normally moves away when I try to hold or handle her, but she has been like this since she was a kitten, so this is normal behavior for her. Her eating, drinking, sleeping, and playing are all normal. Could this be a normal part of her anatomy, or could it be a lump that needs to be checked? Could it still be related to her rabies vaccination even though I only noticed it recently?