I agree with Bostontrevor. My friend's scandium MTB Frame had a similar dent in the same area. He talked to the framebuilder who, upon inspection, advised him to replace the frameset.
I think of it like an aluminum can. An AL can will support my weight if its shape and integrity is still cylindrical. However, if I place a small dent in the side and then try once again to balance atop of it, it will collapse instantanously.