canker(?) sore in back of throat?

i gave my bf head and i swallowed the other day and hes a fairly clean guy, and ive done this before w him for longer w no issue.

just recently ive been feeling a pain in the back of my throat that looks like this

i think its a cankersore? it feels like one and ive been very prone to them in the past. any idea what it could be? im his first girlfriend and we’re both 16 and confused bc this hasnt happened before.