You absolutely do NOT have to do anything that is bringing you pain. If you are sore you should take a break and heal. Are they doing too much suction on the latch? Are you hurting during or noticing it more post?
I see that you are approaching this from a service sub angle. Some Doms can be very rough and have “using you” energy immediately, rather than titrating to your level of experience and need. Even if you aren’t with a Dom now, I’m suspecting these encounters might be with an inexperienced or less than gentle partner. Please take care of yourself. There is this assumption that subs, even masochistic ones, are supposed to be in pain all the time and enjoy it. That is NOT true.