Hard to exactly tell from your picture given.., but my XJ had the same kind of damage to the front bumper when I bought it. Took the bumper off, separated a few parts, and beat them with a big hammer, on the concrete floor, and even used a 6" bench vise, pry bars, etc., in order to straighten parts, including the bumper. All in all, straightened out everything using the above alternating methods. Used OSPHO to protect the raw worked metal, primed, painted, and done. Your work should be less, since you only have a little piece, or two to deal with. Take your time, relax.
After one season of driving, and considering how easy the OEM bumper crushes in such minor instances, I ditched it for an ARB winch bull bumper for it's additional useages. However, you might want to consider a 'real' bumper, and there are plenty of styles, and offerings.., in fact there are those here at
who will offer to sell you one, either mass manufactured, or homemade. I think the OEM bumper is worthless, except if you are trying to keep the XJ absolutely stock for some future selling point.., i.e., an idea that is moot these days... I keep the OEM bumper in my ditch, lol, in case I decide to sell the present XJ for another one, and want to switch 'em out, (whatever the better bumper), keeping the ARB setup for the 'newer' XJ, etc.
If I remember correctly, lol, bit skeptical about that, lol, you will/could need a couple of jack stands, and a floor jack in order to assist in muscling major parts up/down, and all around. Also, while you are at it, you might want to consider a couple of $75.00 tow hooks.., although that will probably entail using some more hammering, prying, and maybe even some drilling.., as I found in trying to get the hook/parts to line up correctly after the incident damage like yours. Good luck, and take it easy.