Looks like paronychia (pus formation in the nail bed)
Is it painful, is the thumb feels warm to touch? If so it's paronychia,
You need to consult surgeon for incision and drainage of pus.
Next Steps
take tab chymoral forte 1-1-1 (after food)
hot fomentation
consult for any query
Health Tips
maintain local hygine.
if the pus comes out apply betadine ointment.