The problems men least want to bring up, which is exactly why they go untreated for years.
Peyronie's disease
Scar tissue forms in the wall of the erectile body, producing curvature, sometimes pain, and often shortening. It typically has an active phase where the curve is changing and pain may be present, then a stable phase.
Treatment differs depending on which phase you are in, which is why being seen while it is still evolving matters. Options range from off label gels such as verapamil, which need to absorb through the skin, to injections into the plaque, to surgical correction for stable, significant curvature.
Phimosis and foreskin problems
A foreskin that will not retract, or will not return to position, can cause hygiene difficulty, pain with erections, and recurrent inflammation. Some cases respond to topical treatment. Others need a procedure.
Balanitis
Inflammation of the head of the penis, often from infection, irritation or poor drying under the foreskin. Recurrent episodes deserve a look at whether diabetes is contributing, because it frequently is.
Priapism
An erection lasting more than four hours is a medical emergency, not an embarrassment. Prolonged episodes cause permanent damage to the erectile tissue. Go to an emergency department rather than waiting it out.
Men with sickle cell disease are at particular risk, and so are men using penile injection therapy, men taking certain psychiatric medications such as trazodone and some antipsychotics, and users of cocaine and other stimulants.
Lumps, lesions and skin changes
Anything new on the penis should be looked at. Most turn out to be benign, but penile cancer is far more treatable early, and the ones that are missed are usually the ones that were too awkward to mention.