Welcome to the board.
Don't worry about the STIR. It is just technical jargon for something they can do with MRI technology to make it easier to "see" at the cellular level. It stands for short-tau inversion recovery (STIR).
The lesions are something that should be noted on the radiology report, but is nothing to worry about.
The "bone island" is an area of benign cell growth of either bone or cartilage that shows up in the middle of a bone. It usually doesn't cause any pain and is only discovered when imaging is done for some other purpose. They can sometimes cause pain after strenuous exercise, especially when the bone island is in a long bone like the thigh. I would be surprised if it caused pain in a vertebra...but then, we members are not doctors, so surprise is always possible.
Your symptoms do make sense for someone with a disc bulge that is compressing the L2 traversing nerve root. If you want to see a general pattern of how the spinal nerve innervates a particular area, just look online for a dermatome map. You will see where the nerves for L1 and L2 go.
Hopefully with some PT and careful body mechanics and good posture, etc. you will be able to heal the disc herniation. If you continue to have issues, you will want to see a spine specialist for an accurate diagnosis for your back problems.