Hello Dear and thanks for the query
Any lump which fulfills the following criteria needs a medical attention:
1. If lump is painful?
2. Lump increasing in shape and size?
3. If there is any kind of discharge from the lump.
or swelling over the lump.
As you have explained the lump is painful you need to get examined by your doctor and get treated according to the diagnosis. You may need a course of antibiotic to recover form it.