I found a pegions egg ?

one pegion laid an egg today morning but the mother did,nt came afternoon and now its evening and it is getting and it is raining and the egg got little wet what can i do to keep it warm and how can i hatch it without incubator how can i kep it warm at 100 degres f the mom will not come back becaue my younger brother had tuched the egg what to do please help