If it's not accompanied by lower back pain and cramps I'd say you were ok! I had some spotting at 12 weeks and I found out I had a subchorionic hemorrhage but was very tiny. It's more common than you think and can cause bleeding. Another thing is it's very very common to have a low lying placenta in early preg because it hasn't migrated up yet. As the baby bounces on the placenta it can cause a small bleed.
Relax, stay hydrated and rest! If you have questions I am here. Remember- bleeding in the first trimester is very common. If it continues talk to your doctor, if accompanied with bad cramps I suggest a er trip that way a scan can be done to check!