Sharp hip inner groin pain - indoor bike

I think hip pain inner groin could be too flexed a position, if it means you are finding the natural limit of how far your hip can flex. Are the bars lower/saddle further back/saddle higher or cranks longer?

When I've had it more recently it was because the saddle was too 'nose up'. Didn't take much either.

not had that but even on a "normal" setup, your position is often very static when indoors.  I have a tilty base for my turbo but it's still not like riding outside

I'm guessing that a setup like yours is even more fixed, so maybe stressing some muscle groups differently (esp/including the little ones in yr groin)

If you're newish to the setup, maybe take it easy until you've improved the flexibility/resilience of your relevant bits

I'd start by using a spirit level to check that your saddle is still at the same angle on the trainer as it is outside - I recently developed a bit of a sore spot and apart from the saddle being knackered from tens of thousands of km, it was also slightly nose up on the trainer. I changed the saddle and levelled it out by putting some cardboard packing under the rear rocker plate and it's now appreciably better. 

As others have said, the static nature of an indoor trainer amplifies any fit issues. If you're not doing already, make an effort to get out of the saddle for a while every ten minutes or so. I suspect the optimum answer would be to have a bike fit, particularly if it's a road bike, but it's quite an expensive option. 

Thanks. I have been riding on it for 6 months now but recently completely upped the intensity. Have toyed with getting a rocker plate as it very stiff but at 70 kilos it's one hell of a beast.