Is there any pain to it? Where on your penis is it located?
Veins are normal on the penis, and sometimes they are more noticeable than other times. https://www.healthline.com/health/mens-health/veiny-penis#reasons-for-prominent-veins
It might also be a lymphocele, which happens when the lymph channels in your penis are temporarily blocked, usually after sex or masturbation. It's temporary and goes away. This link has graphic medical penis pics, so open when you're alone, or skip it if someone monitors your phone use:
It could also be Fordyce spots, which are oil glands, and also totally normal.
Do you have an adult you can talk to? A parent, older sibling, aunt or uncle - anyone? I don't think there's a big reason for concern, but it would be great if you had someone who could take you to the doctor if this doesn't go away. Don't masturbate for a couple of days, and see how it feels.
Let us know what happens. :)
Ya, I think this is probably a normal vein you are just now noticing. Even if it is slightly more pronounced now than before, it still can be normal. If it is lymphocele, it should also resolve. If not, At 15 do you go to the doctor once a year? At that time, you can mention this. Don't be embarrassed. We get morning erections so certainly by this time, your doctor knows you have examined your own erection and it is very normal. I also agree with auntiejessie that it would be excellent if you had a trusted person to go to for any and all questions. You'd be surprised the things that all men deal with and your dad or older brother or uncle will be able to be very informative to you.