Depends on the size of the magnet 
No, you will be fine, the xSeries implants have been subjected to many safety tests, including a MRI ( GIANT FUCK OFF MAGNET )
Here is the link to the tests
It would be a different story if you had an xG3 or Titan magnet implant.
The one you have been able to read with your phone is likely an xNT, the other one ( still guessing here ) is likely an xEM, so you wont be able to read that with a phone.
So this woulld explain why you can read it from the palm side, It doesn’t sound like an easy or practical read, personally I would be looking at getting it removed to put back in “where it should be” and take some prenatals to help lock it in place so it doesn’t happen again.
Hopefully you can locate the xEM ( if it is one ) with a magnet or xAC.
Is it possible to get an xRay?
Ideally get an xRay and removed whilst at the doctors office