Thanks for query,
Is is mixed with urine ? if yes than it is an urinary infection if not then
You may have mid cycle spotting.
This happens due to hormonal
The other possibility is of you may have tore your hymen
as it can be torn accidentally by cycling horse riding or by high jump,by fingering etc,
Just wait for day or too if it is mid cycle spotting then it will stop by it's own.
If it is still there you should consult your doctor.