Bray Wyatt’s back injury isn’t “super serious” but it could keep him out of Wrestlemania 32. Sources close to the situation claim Wyatt would have gutted it out if he were in a match against Brock Lesnar but he’s very frustrated about being the odd man out and doesn’t want to rush anything when there isn’t a big match for him.
This is similar to Sting’s situation, although Sting’s condition is much more. Sting did want to do one last match against The Undertaker but with that out the window, he just didn’t want to take the risk. Before Wyatt got hurt, WWE did try to make Wyatt vs. Sting happen for Wrestlemania, but Sting wasn't interested. So Wyatt ended up with nothing of consequence and now may not wrestle at all.