Possible melanoma?

Breed: Mixed Pomeranian/Chihuahua Age: Approx. 10 years old Weight: 11lbs He is not neutered So, my dog has a bit going on. Prostatitis along with a cyst (diagnosed through ultrasound), a grade 4 heart murmur, and 2 different types of arrhythmias (that the cardiologist suggested we test for Chagas). And cystitis which has been explained could be caused by the prostate issues. So he’s going to the vet much more than usual and I’ve been anxiously watching for any potential symptoms. I had noticed previously that he had some penis discharge & the vet didn’t seem to concerned, said it might be allergies (?) and to keep my eye on it. Since he has been licking his groin I checked and noticed this dark bump on his penis. Is this worth a vet visit or am I tripping? https://imgur.com/a/ZXwAElt

Hello - I'm afraid that it's very difficult to tell from this image what we are looking at.  Your vet will be able to assess the change in person, in three dimensions and touch the lesion too, which will give them much more information.  The symptom of licking the groin may be connected to pain - either at skin level or deeper e.g. the bladder - or itchiness and generally should be investigated.  A a symptom, licking is relatively rarely associated with cancer - there are many more possibilities, some of which may be addressed even with symptomatic treatment.  A vets' appointment could therefore prove worthwhile.   Please will you let us know how you get on?

Sorry as I'm still unsure if dog moms with no science knowledge cam comment. As a mom of long time vag licking medically complex dog with extensive oncology and cardiology specialist history- and I dont mean ever to suggest I know anything- but curious as to why chagas- right side, climate? I would just also possibly ask about babesia and bartonella (which arent treated by doxy- like erhlichia). I hope he's made a quick recovery- it sounds like you have great vet care