damaging obsidian

I was mining in minecraft pocket edition and i found a cave with water and lava . I stopped the water and i stept on the obsidian . I had a little lag spike first time and i saw that my health went down . I was curious why my health got down to almost a half , so i stept on obsidian again i got damaged again so i went back to my base . I imediatelly get on this forum and wrote this message . I hope that Herobrine isn't starting to strike on minecraft pocket edition 😧 . I also forgot to say that i have a LG L70 .

I was mining in minecraft pocket edition and i found a cave with water and lava . I stopped the water and i stept on the obsidian . I had a little lag spike first time and i saw that my health went down . I was curious why my health got down to almost a half , so i stept on obsidian again i got damaged again so i went back to my base . I imediatelly get on this forum and wrote this message . I hope that Herobrine isn't starting to strike on minecraft pocket edition 😉 . I also forgot to say that i have a LG L70 . Some hours later i discovered that not only obsidian damages . I was walking in a cave again and i took random damage while mining coal from a wall. I think there are invisible blocks/mobs . I hope you can do something about it .