hello, im 16 years old

Over the last 2 days my left testicle has been very tender and feels swolen. I have also noticed that I have a lump just above that testicle, where it connects to the sperm tube. The lump it'self is not painful but the testicle is. It is rather large and feels soft an squidgy. Over the past two days my girlfriend has sat on my groin area a lot. This isnt in any sexual way but she did ask "am I squishing you?". I did not think she was at the time, but later on I realised the swelling and lump.

Sorry there is not much infromation to go by there, but could someone please help me out with advice or any ideas what it may be.

I do not with to tell my parents, not yet at least, but I have considered seeing my doctor about it, which I'm also not overly keen on.

Thankyou for any help.