Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services for trouble breathing, facial or throat swelling, faintness or another sign of a severe allergic reaction after using medicine.
Seek prompt medical advice if you are pregnant, have a weakened immune system, or notice a hard, ulcerated, darkly pigmented or persistently bleeding growth.
Get urgent medical help if swelling or growths make it difficult to pass urine, or if you develop severe pain, spreading redness, pus or fever after a procedure.
Arrange a routine appointment with primary care or a sexual health clinic for new genital or anal bumps, persistent itching, unexplained bleeding or an uncertain growth.
Seek assessment if a sexual partner has genital warts or another sexually transmitted infection.
The article also says
Contact a clinician if treatment causes marked pain, open sores or irritation that does not settle.
Assessment is also important if warts recur, grow rapidly or do not improve with treatment.
Every sign above is quoted from the sofidex article on Genital warts. If you are not sure, err upward — it is always reasonable to be checked.