How do you straighten new steel rims?

I just laced up a new rear rim from a seller on Ebay. Some no-name brand rim. It's pretty off at the butt weld, like a dip in the wheel. I have the spokes in that area pretty tight, any tighter and I'm afraid something will strip. Can I try to hammer the dip out?

I laced MX wheels alot of times before with no problems but they are aluminum.

How are you trying to tru the rim up? Is the rim warped or more like an out of round situation?

I have a homemade truing stand that I built a bunch of wheels on.

There seems to be a 'bump' in the wheel where the weld is. About 5 spokes in duration. I have those spokes as tight as I would go but I cant get the bump to budge. The rest of the wheel is 'ok' to where I can work with it, mostly side to side out of true.