Mycobacterium species like Mycobacterium tuberculosis do not form endospores. Therefore no endospores can appear. Endospore forming bacteria belong to the species Bacillus or Clostridium. Whatever you see is (i) either not an endospore or (ii) the bacterium is not a Mycobacterium. Mycobacterium can survive within phagolysosomes, but they absolutely do not form endospores.