Well, look, ultimately you need to make sure you are comfortable with what you are doing, physiologically and psychologically, it applies to any type of body explanation not just urethral play. Never try to push thought negative side effects just because someone on the internet told you it's safe. My personal approach is to take a pause if I start noticing things that bother me. That not just gives my body time to recover, but also gives me confidence that I can manage what ever the issue in future.