There are many ways in which you can learn to help yourself help your pet in times of sudden illness or injury. Although it's always best to run this by your homeopath, if you cannot reach him in an emergency, there is still much you can do safely.
Here's a nice example: last week my dog became lame in a rear leg some time after a vigorous exercise session. Her unwillingness to use the leg was the only real symptom - there was no obvious joint damage or anything she couldn't actually do with the leg. Assuming it was a soft tissue injury, and ruling out a completely torn ligament, I gave Arnica for any swelling and bruising, and then the more specific Ruta Graveolens, which loves sprains and strains. I also used an ice pack on it at intervals. After a few days she was using the leg but still favoring it, and I noticed it was worse upon arising after a rest or sleep. Well, heck, there's a remedy that does exactly that, Rhus Tox. This morning I gave her one dose, and she soon showed no signs of favoring the leg at all, and was quite active all day. I love it when it works like that!
This is not to tell you specific remedies to use, but only to illustrate what a working knowledge and a first aid kit can do. This part ISN'T rocket science, and can be mastered with a good book or short course. The only problem is that, as soon as you start seeing these little miracles you'll want to keep on learning more:)