Pain after erection

I've been on trimix for a couple of months now and I'm wondering if it's normal for the tissue that's deep in the penis to hurt after the erection has subsided?

When my erection is about half gone I'm still firm if I press straight in on the glans but it is very sore.

I normally get an erection for about two hours but there is still firmness deep inside for hours after that. My urologist tells me that it's no big deal but the entire penis is sore for hours after the injection.

So I'm just curious if this is normal?