I replaced all my ball joints and tie rods on my 98 Blazer. It went easier than I thought it would, except for the last ball joint. It's not sitting on the knuckle as do the other ones. Is this ok to leave it installed or do I need to change it out again?

Looks like there might be a burr or some obstruction not letting it settle into place. I would look further into it to be safe. It is unlikely but that rubber could be short and you are fine then. That said,, better safe than sorry.

Thanks for the reply. No burrs I inspected before installing it. Is the rubber boot suppose to sit flat on the knuckle?

yes it is supposed to sit solid between the joint as a weather seal and to hold in grease better.