Hi thanks for your question.Your having a lump in groin and it is growing very fast.Well there are few possibilities what this lump could be;
The No 1 possibilitycould be inguinal hernia
which has been ruled out.The second possibility could be an enlarged lymh node and third possibility could be a lipoma
.Fourth and final could be a boil,but boil will give you pain and fever
which you don't have.Since you are going for ultrasould tomarrow,it will help your Doctor in determing what exactly this lump is.Ultrasound
supported with,FNAC and blood will work help in establishing the diagnosis.
Hope this answers your question.