First... relax. You can "what if" yourself too much.
A quick fix could be using a rain jacket or poncho to cover the area from the outside, as you'll need to cover over the hole, until the situation allows you to make better repairs.
If this isn't possible, you could go to rigging something underneath as a means to divert the water flow away from you. If you used a CRL for your tarp your ridgeline will be of great value here, depending on if it's under or over the tarp. If not, a quickly tied line, say from your bear bag, would work.