This has happened before and if you have not started the motor you should be fine, however it is going to cost you lots of oil and a few filters. I would suggest the following.
1. Completely drain the motor oil and remove the filter. Check the oil and filter for Antifreeze.
2. Install new filter and refill the motor with the correct amount of oil. Let sit for a few hours and then drain the motor oil and replace the filter for the second time. The reason you are doing this is to duplicate the path of the antifreeze when it was poured in. it should flush any remaining antifreezes to the pan and filter.
3. Install new filter and refill engine oil.
After a few miles I would remove an oil sample and send it in to be analyzed. Here is a company that will analyze your oil if you don't know one.
I am not a mechanic so this is just a summary of thing I've read on the subject. I also do not work for Blackstone Labs and only found them while doing a google search for oil testing.
Good Luck and let us know how it turns out.