What you can do next time you plan on a making a card is to not tear the blister off the card. Instead, use acetone (found in nail polish remover), and use it to take off the blister. Youtube videos of it if you're not familiar with how it's done. If you get any of the paper still on the blister, put on some more acetone and scrape it off with whatever you got.
When you're applying the glue, make sure you get some flat object, one that is large enough to cover the whole card and is of a structure. You want to make sure it doesn't bend or warp in any way. If it isn't already heavy, get a heavy object you can place on top and let gravity do the clamping job for you. Let it sit for an hour at least.
Also, when you're printing, do leave a margin of space outside the print area... "bleeding" as graphic designers call it. This will help reduce the possibility of seeing any edges when trimming excess. Plus this means there is a bit of lenience when putting the print down on the HW card.