My calf muscle popped while i was boxing. i can't take a full step without a lot of pain. should i go to the er tonight to have it checked?

As soon as possible: You should see a physician as soon as possible, but likely going tonight won`t help. Most of the time, a "pop" is associated with a torn ligament or cartilage. Get in to see a doctor in the morning or tonight if you have worsening pain.

Tendon pop: You might have ruptured your achilles. Get into the er tonight to be properly evaluated and immobilized. Make sure to get a referral to a podiatrist in your area for follow up.

Probably not: The er will probably not be able to do anything to help your problem. It is probably just a calf muscle strain/tear but it could also be a torn achilles tendon. If while laying on your stomach, someone squeezes your calf and your foot does not point then you will need to see an orthopedic surgeon (google thompson test).

Ruptured Achiles: Sounds painful. You may have ruptured your achilles' tendon. If the calf muscle is torn, the torn section will contract and shorten. This may make it impossible to reattach if too much time has gone by since injury. Also, the remaining muscle will be at risk for further tearing. Try to see a doctor asap. Waiting could make any repairs more difficult. Good luck.