the tip is only there to protect the pintile. if it's cracked and may come off i'd just remove it and be careful w/ the injectors to not drop or hit them while installing them. if you bend the pintile it may jam or not deliver fuel properly.

one of mine is missing, it cracked when i was removing them during emissions time and smacked it against the valve cover. luckily it was there, but it split it. i removed it, checked to make sure the pintile didn't get damaged and reinstalled it. no issues yet.