My cat has a large soft lump on the right side of his stomach?

I was petting my cat this morning and noticed a tumer like lump on his side. It feel a little like a fat tumor (my childhood dog had fat tumors as he got older) but i cant really tell because my cat has always hated having his belly rubed. Should i be worried? What could it be? Is it urgent for me to take him to the vet? Im only 16 and my dad works all week so i dont know when we could get him in the vet... Has anyone else delt with something like this before?

I don't think it is extremely urgent but if I were you I would try to get your dad to take the cat to the vet as soon as possible. It's always better to check these things sooner rather than later. Fingers crossed it's nothing serious