bruising from injections

I have been injecting Lovenox twice daily for 12 days now and have experienced slight bruising at a few of the injection sites until this morning. My injection bled just a drop when I withdrew the syringe but it has stopped just a few minutes later. I looked at the injection site at noon today and saw an area about 30 mm in diameter, raised about 10 mm that felt hard. I assume I had been bleeding under the skin surface for quite a while this morning.