It could be an abscess, or a lipoma (which is benign, but can press on nerves nearby) If it is touchy and painful, it is possible it could be an abscess
. Sometimes, even lipomas are sensitive. Lots of lumps are not necessarily cancer. My dog
is lumpy as a rice pudding, but they are not malignant.
There is only one way to find out....,.go see the vet! If by any chance it happened to be a malignant lump, the best plan would be to have it taken off as soon as possible.