Hi mate. I know it's more than a year ago since your post and I hope you're all right now, but this is just a post to help anyone who comes across this post.
I am 19 and I went to the GP about a very similar feeling.
I have a constant warm sensation in my left testicle.
The doctor said it's nothing to worry about and it's quite common. He said it could be a minor infection which will sort itself out in its own time.
As long as there is no severe pain or problems urinating such as difficulty or discharge, you don't need too worry.
If it's painful or uncomfortable but no other problems, you can take some regular high street painkillers such as nurofen.
Hope this helps anyone out there.