This is a very common injury for the way you describe the incident occurred. More than likely, you have a strain to your Achilles tendon. This is the tendon that goes from your calf muscle down to your heel. It allows you to plantar flex, or push your foot downward, like you do when pushing on the gas pedal.
The concern is for a tendon rupture. It is likely that it is NOT ruptured, because you can still walk fairly well. Here is one test you can do, either alone or with help. Stand by a chair and place the leg that is injured on the chair, with your knee bent at 90 degrees. Then squeeze your calf. If your foot moves downward slightly, then the Achilles tendon is intact. If you have help, then lie down with your foot hanging off the edge of the bed, and have your assistant squeeze your calf. They can look for the motion in your foot. It is important to relax your leg with either of these maneuvers.
Either way, do not try to do calf raises for a few weeks. You likely have at least a significant sprain and it will takes 4 - 6 weeks to heal completely, possibly a little longer. It is advisable to seek medical help if it does not continue to improve.