Help sony xperia m gets hot


Please can anyone help, being new to the forum and phones, I had the Sony Xperia m and its been good, it's 6 month's old, two weeks ago it for very hot 136

I factory reset it, but then it stopped charging, went for repair ,exchanged the main unit, it's works ok but I feel still hot 42c 110f when downloading and removing apps, it cools down to 30c 88f

Is it normal,ok to use, is it me,can anyone help,is it an app running

Any help please