You can save an ink cartridge that has been mistakenly opened

It will not work 100% but it can help, and it can buy you some time. You may want to try to save it by taking a damp paper towel, remember to rinse it out completely, the put the paper towel and the cartridge in a tightly sealed bag. The important thing is to keep the moisture in the bag (no water). The moisture keeps the cartridge from drying out completly, once you have it in a bag, keep it in a cool place, and check on it periodically, if you see that the paper towel is drying out, remoisten it. If you still have the blue tape that sealed the cartridge, obviously it is preferred, but this method at least will keep the cartidge usable for a few months if the towel is not left to dry out.