The painful lump beneath the nipple and tonsillitis
are not related by any means. Both are independent conditions, requiring different treatment.
Yes, you should be concerned about the lump under your nipple. It seems to be an infective condition. You need to take antibiotics which will fight the infection. Also add some analgesics and anti inflammatory agents which will reduce the pain and inflammation.
After a week of this treatment, if there is no response, you have to consult a surgeon .