There are a lot of capillaries and small vessels that may bleed after the needle is removed. They are small enough that when you pull back, it collapses the vessel. usually you aren't in the vessel anyway but have ruptured some small skin capillaries on the way in that will bleed after you remove the needle.
Fat also has a lot of small vessels, so if there is fat over the muscle, the vessels in there can be ruptured and bleed. Usually the bleeding is a small amount and as the others have said, a bandaid is all you need.
If, after the next injection you get any symptoms of sweating, anxiety etc., tell your Dr. Some people are allergic to the cotton seed oil or sesame oil that the hormones are mixed in. Its not worth risking an anaphylactic reaction to the drug. Not all serious reactions happen the first or even second time, so even if you think it isn't serious, tell your Dr.
sam1234