I am trying to follow what you say is going on. You are having nerves or probably more accurately veins that you can see? (you aren't going to see nerves). You have no pain in the penis but sometimes in your left testicle? This has been going on for 5 months. Correct? I just want to check the information to make sure I am understanding. Here is an article to read. https://www.healthline.com/health/mens-health/veiny-penis So, this is either normal or you have to look at why it is happening. Varicocele is one reason to look into if this is not normal. This can be a dull ache. However, you also may have a blood clot. In reading this article, you may identify with that information. This includes that it is a new swelling in the vein, worse when erect and pain when erect. Have you had any trauma or injury? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2978449/ If this continues, it may be wise to see your doctor to discuss.