You might find that some of the spray has made its way into the hook mechanism. You may have to clean out the bobbin case and the hook assembly. Skipped stitches mean that the hook hasn't picked up the upper thread. If the loop of the upper thread was caused simply by the thread not making its way out of the eye of the needle, because the eye of the needle is gummed up, you may be OK. You'll have to clean the needle, and perhaps change it if it can't be cleaned. If the spray however got onto the hook, at a minimum, the point of the hook may be gummed up.