Hello,
There are many causes for vomiting and many are acute and transient and do not require a trip to the ER. In general we recommend that you not give your pet any food or water for about 12 hours to let the stomach and gi tract rest. The only concern with this is if there is a chance your cat is dehydrated. If your cat is acting normally and the gums are moist and the skin turgor is normal (this is the amount of skin tent in the area of the shoulders) then they are likely not dehydrated. If the vomiting persists in spite of with holding food and water, or if your cat appears to be quiet, lethargic, depressed or cannot stop vomiting, then yes a trip to the vet is in order.
Look around the house to make sure that your cat hasn’t eaten anything inappropriate or dangerous like any kind of toxin (plants, toys, rotten food, etc). If an accidental ingestion is possible this warrants an immediate trip to the vet for care.
If the vomiting stops over the 12 hours i recommend offering small amounts of watered down wet food every 3-4 hours starting tomorrow. If the vomiting returns see the vet.
Best of luck!
Merry Christmas!
Without knowing the extent of the injury all I can advise is to try to keep her quiet and calm and monitor for any trouble breathing or discomfort. Signs of breathing difficultly, trouble walking, dissension of the abdomen, bleeding, changes in attitude that include panting, inability to get comfortable, or any sign of distress warrant an immediate trip to the closest emergency clinic. Please see the vet tomorrow and I expect they will do a thorough exam and provide pain medication (please don’t use an over the counter without the vets ok), and antibiotics.