Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency medical care now if you develop sudden fever with a painful swollen lymph node after:
Tell emergency staff about the possible exposure before or as soon as you arrive.
Call emergency services for breathing difficulty, chest pain, bloody mucus, confusion, fainting, unusual bleeding, blue or darkened skin, or rapidly worsening weakness.
Routine follow-up after treatment is different from emergency care.
It may cover recovery, healing lymph nodes, test results, medication effects, and any longer-term complications.
Do not wait for symptoms to become severe.
If you are already receiving treatment, seek prompt medical advice if fever returns, the bubo becomes more painful or starts draining, you cannot keep medicine down, or you develop a possible medication reaction.
This helps them arrange suitable testing and precautions.
Every sign above is quoted from the sofidex article on Glandular plague. If you are not sure, err upward — it is always reasonable to be checked.