Hi thanks for question,
You’re having soreness and lump above your umbilicus
you cannot feel it when you lie dawn.
It is associated with burning sensation and now nausea
off and on.
From the symptom you have described it looks to be an epigastric hernia
, through which part of your stomach herniates when you stand up and disappear when you lie dawn.
The herniated portion of stomach is giving you burning sensation, nausea and pain.
Get yourself examined by surgeon to know what exactly it is.
Hope I answered your question.