This topic has been well discussed in the past. That stated, an erection, a semi, or leaking pre-cum is a normal reaction to an examination for a hernia, the digital prostrate, etc.
I have been a teaching associate at a medical school. Our teacher instructed us to say to the medical students if an erection happened, or a semi appeared or pre-cum leaked out to remind the student that it was a normal reaction.
In fact we told the students that the best comment to offer was something like:
It seems that everything is working as it should.
Please bear in mind that about half of the medical students now are females.
No problem. The training was conducted with groups of four or five students in each session. Of course there were boys and girls in each group. Also, the training was recorded so no one could say anything was inappropriate. This was for the protection of both the teaching associate and also the students.
No problem.