It would be normal if you used something that caused your tender tissues to bleed. For example, sometimes young women write in that they used a hairbrush handle, and I would imagine that going at it too vigorously with such a hard object might cause bleeding. (Using a hairbrush handle is a terrible idea for masturbation, not only for this reason but also because it is probably not going to be clean enough.)
But sometimes a woman also has bleeding from her period that arrives at an unexpected time of the month, and if it is coincidentally also around the time she had last masturbated, she worries that she is bleeding from the masturbation and not the period. If this continues, it might be your period.
Try not to worry, either you caused the bleeding by masturbating, in which case it will doubtless heal, or it's your period.