B’sha’ah tovah!
Yes, that does make you
niddah. Any amount of blood found on something inserted internally, like a tampon, can make a woman
niddah. The leniency for stains smaller than a
gris applies only to stains found externally (learn more
here).
For the future, if you want to use protection just in case your period comes, we recommend using a
disposable pad. Since the pad is external, all the
leniencies of stains would apply, and a
small quantity of bleeding would not make you
niddah.
Please feel free to get back to us with any further questions.