Waiting is hell! However this short time will make no difference to the outcome so try and relax. The core biopsy is a little uncomfortable but perfectly bearable as you will have a local anaesthetic. Very soon you will know. There is nothing to fear but the fear itself... Lots can be done these days even if the result is +ve. Hang in there and good luck
You could indeed have a cancerous nodule but you could also have a benign nodule. The biopsy will give you the answers to this question. A biopsy is the ONLY way to determine the nature of any abnormal finding in the breast. One important thing to remember for the future is that only the Radiologist that reads your films can tell you if everything is alright or if something needs further investigation. We are always concerned when something isn't right and we all worry about it. Everyone says the waiting is the worst but it's something that we must learn to do as patiently as possible. The pain you describe may have nothing to do with the nodule that was found on Mammogram. Please feel free to ask whatever concerns you regarding your biopsy. Regards....