What could this issue be?

My best friend has a red pimple on her stomach and it's been there for several weeks. We don't know what it is, it doesn't itch or turn pale when she presses on it. She thinks that the red pimple could have came from her lifting a heavy suitcase, but we still don't know. And it also hurts a little when she touches it. Could you help us and figure out what the cause of this is?