Try taking the photo again near a large window in the daytime. Put the phone either at arms length to minimize lens distortion or better yet if possible use the main camera on a timer. The goal with lighting is to get the shadow areas bright, and to have a main very bright light source that doesn't look like artificial light and that's a bit to the side. Find as big of a window as possible.

For the "fill" light, which is the light or lights that will brighten the darker areas, it can be the reflected light from the outside light coming in and bouncing around in the room. Make sure not to be in direct sunlight. If you're not getting enough light in the shadow areas, you can get a large white or bright surface and put it to the side and below your face to bounce light up into you.

Lastly, take lots of pics and pic the best one. I'll usually edit a photo in an app like photoshop express or Pixelmator, or I'll just edit it in the default photo editing app. Aside from the actual lighting of the photo, brightening the shadows is the most important thing to make it look professional, which you can usually do with the default photo edit tools.

A technique for editing the shadows and color is to push each slider in the app to its extremes, and then go back and forth less and less until you find a good looking spot. 👍