The lower back is a tricky thing. Be sure to have a qualified doc take a good look at your MRI. I know back pain also, been living with it, every day, for years. I have a degenertive disc in the L5 that puts pressure on the cyitic nerve. There is one constant in my life-my back is going to hurt- it just varies in intensity from day to day. My doc didn't sugar coat it. He said him himself lives with the same condition and you deal with it untill it starts effecting your daily life then you have to explore your options. The trick is to not damage the sheathing around the nerve as that will not repair itself-ever. Nerve pain is no joke, throw in some 2x4 snapping spasm's and your in for a grand ole time.
Get it checked out and keep an eye on it. I don't know how much shooting a bow lends into it ( I mainly use upper back while shooting). Keep your core strong and use your head when lifting heavy items. Don't be bull headed. If it's heavy, get another set of hands involved. Heck, I remember I bent over to turn the water spicot on and was laid out flat on the sidewalk. Took over a week to recover from that one. Simple things get you sometimes for no rhyme or reason. Hope it's something simple and you recover quickly and fully.
Regards