Well, you may be up the creek.
From other similar threads here, it seems that when people install Swiftkey (or similar third-party keyboards), they often disable all other input methods. Later, if they uninstall the third-party keyboard (or crash it as may have happened in your case), the system has no other enabled keyboards and you fall into the trap you are in now.
Sadly, it seems the only real option at this point is a factory reset but don't take my word for it. Search other threads and/or wait for confirmation from another top user.