Assalaamu alaykum. I entered the masjid with a cut on my big toe that nearly goes completely under my toe. Before walking in, I thoroughly checked to make sure that there was no blood coming out of the wound. During the prayer, I felt some pain in my foot. When I walked out of the masjid, I saw blood on the inside of my wound. I also saw a little bit of bloody sand on the inside and the outside of the wound. I then walked back in to sit and see if I was really bleeding. I then went back to the area where I had prayed with a flashlight and searched for any signs of blood. I knew that I would not find any, however, since the blood had not been flowing, and also because grains of bloody sand are nearly impossible to see. That said, even if there had been blood in the masjid, would I be held responsible for that? Please shed some knowledge on this. May Allaah reward you.

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger. 

The majority of the scholars held that an insignificant amount of blood is considered an insignificant impurity that is excused and pardoned. Therefore, the matter is simple. Assuming that the blood touched the spot where you were praying or that blood came out of you and stained your body during the prayer, your prayer is still valid and you are not liable for anything. The basic principle is that nothing came out of you. You should adhere to the basic principle and act upon it.

Allah knows best.