That really sounds like a hernia to me. You should be able to push the lump back in, that might give you some relief from the pain. You should go to your physician asap to get a diagnosis and I would lay off the rowing maybe as well until you have spoken to one.
No heavy lifting is advised as well, so don't do that just now either.

I had my third hernia just four months ago and managed to get it under control by taking hawthorn, silicea and doing reflexzone massages on my feet at the beginning. I only done the massages for about 10 days which helped the intestine to recede back into my stomach and since then I have only had pain in my groin rarely after putting strain on it.
I haven't done any sport yet but I manage to lift slightly heavy things again without my intestine protruding.
I will start swimming again in approximately two weeks time and then start exercising properly again after I see how I get on.

I am only telling you this because I had three hernias all on the right side, two operations and it still was recurrent. Hernia operations aren't the most pleasant thing to have since you are pretty much immobile for a t least one week post op and you cant do any sports for a couple of weeks either depending on the method they use. I still had pains in my groin area after both operations too, years later, so it is not that you will be completely repaired afterwards either.

I am not advising you not to have an operation, definatly consult with a doctor, maybe they will even just give you antibiotics and lie you down for a couple of weeks depending on how bad the hernia is.

I am just saying that there is an alternative, whether it works for everyone I don't know but it has worked for me so far and I will keep everyone posted on how I get on when I exercise again.
The only thing with what I do is that it takes patience and you should maybe not exercise either, but taking the hawthorn probably can't do any harm whatever you decide anyway, it may relief some symptoms, who knows. Check that with your gp first too though because it is a heart stimulant and I think might interact with other medicines.

Good luck and I hope that you can go rowing again soon, but please do go and see a doctor as soon as possible!
Sometimes they can get strangulated, which can be life threatening, so when you can't push the bulge back in and it gets hard and red and I imagine very painful you should go to a hospital immediatly and tell them about it.
Don't worry about it though, I had my hernias for years before they got diagnosed and went horse riding and stuff, apparently one of the worst exercises you can do to get it strangulated. The surgeon nearly freaked when I told him. :-)

take care and let us know how you are getting on and I hope I didn't go on too much there, it's just that I regretted twice that I wasn't better informed about hernias and what options there are.

Lena