How long has the swelling been there for & how long have you been on minocycline
Only in few postmarketing studies prolonged use of minocycline has been associated with thyroid cancer
which would cause swelling in front part of neck.
Considering description of your symptoms I feel swelling under ear lobe is likely to be lymph
node enlargement - in due course it will need to be checked by Dr to confirm diagnosis but monitor for change in size, shape , feel & colour of overlying skin - if any worsening you will need consultation with medical professional.