Can you post a picture of it?

Russ gave good advise. Leave the plant alone to recover from it's shock. Unless it more than sunburn. Like Russ said, we need a picture to see. If it's a fungus or rot attack. I have a Sans with sunburn and instead of throwing away the leaf, I planted it and now it has some pups coming up.

I figured it was sunburned from the title, supported by the first line, assuming it was purchased from the indoor/protected house plant section of a store. Acclimating to much more sun would need to be done slowly or burning could occur, especially this time of year. Since it's been a month, I wouldn't move it now, if most of it looks OK, it's used to it.

Unless the pot is massive &/or it's rained a few times, a month sounds like a long time w/o water, in the hot sun.

If you cut the leaves at an angle below the burned spots, it shouldn't look too damaged. You can play with propagating the leaf pieces if you want. If so, let them dry at least overnight, then put in a pot or shallow water, burying/submerging the cut end.

Good idea Tiffany, I didn't think about the fact that it might be acclimated already. I sometimes put a new point on sans leaves after cutting off a damaged tip, they always look better for it.

Russ

I'm also sure it's sunburn. Sans aren't really as sun-loving as one would expect. I've burnt them before.

How you deal with it depends on the severity and the conditions your plant will be in afterward. I have just let mine heal on their own. As long as they aren't cold or damp, the burnt spot should just dry up and leave a scar. If it's burnt all the way across a leaf, of course the part cut off from the roots will eventually die off. I'd try propagating from the rescued leaf section.

Sans are very tough though. Get it out of the sun; keep it moist and warm in the growing season, and mostly dry (but not completely) when temperatures drop, and it'll come back from some sunburn just fine.