If you're experienced in such things, then checking the cable for obvious creasing or breaks, and reseating it may help. If you're not experienced, you risk doing more damage by causing a short.
Either way, there's no way for a nozzle to become "stuck open". The peizo acts as a pump, not a valve, and if it's not active it won't allow ink to flow. Hence it's either electrical or electronic causing the head to continuously fire.