Hello and welcome
Surely it is treatable and you need to consult your General physician for that. The lump may be
1. Enlarged lymph
4. Muscle or tissue collection
To get to a diagnosis proper clinical examination is needed and if required FNAC (fine needle aspiration cytology) can be done. Meanwhile take analgesic
drug like Ibuprofen
to reduce pain and you may need a proper antibiotic to get early relief. Consult your doctor for that.