Finishing Question

Awhile back I refinished our dining table. Not too long after I refinished it, it got this ugly scratch on a corner (still not sure how). I had the bright idea to just sand down that area and redo the stain on that part. Suffice it to say, that did not work at all. I sanded off the stain but new stain won't stick (I'm guessing the varnish seeped in) so now I have a lighter patch on the table. If I used stripper, could I just strip the area over the light patch then just redo the stain on that area, or do I need to strip the whole table and start over? I'm really new at this, this was my first stab at staining. Any help would be greatly appreciated.