My dog has a red spot near his penis and is sick. What should I do?

Poor guy. I am so sorry Charlie is ill and has this suspicious erythematous lesion on his belly near his penis. This looks like a possible mild bleeding under the skin or potentially an adverse reaction to a tick or black fly bite. A black fly bite wouln't cause systemic illness however (not eating, lethargy). There is possibly an internal issues going on here and more information is needed to determine what exactly. I would recommend taking him in to the vet first thing in the morning. He should be stable enough to wait until morning as long as she is not having any of the following:
1) Pale gums
2) Severe lethargy and non-responsiveness
3) Excessive vomiting that is continuous
4) More red spots developing on the skin in various places

If he does not show any of the above symptoms, then it is likely ok to wait until morning to get Charlie seen and fully evaluated. The main concern is if there is an underlying bleeding disorder or immune system disoder (i.e. IMHA, IMTP). I hope that things work out well for your pet Charlie and that he feels better soon! The vet will know what to do to treat him once some tests are ran to determine the underlying cause. Best wishes and take are.