it's a lense flare. you point a camera directly at the sun with out any filters and you are going to get lense flares and artifacts. Especially since it's a digital camera in a cell phone, it's not going to be very good quality. If there were an asteroid or planet close enough for you to take a picture with your cell phone, then you would have already known the planet/asteroid was in our solar system; gravitational forces would be off, the magnetic protection around the planet would be off, weather would be going crazy, it would throw other planets in our solar system out of their regular orbit.
Trust me, if there were a planet entering our solar system you would know well before you could take a picture with your cell phone. With as many amateur star gazers there are out there, someone would have said something and there would be stories all over the news about it.