Posted: 05/05/2014 at 19:24
I agree with Tootles - I've renovated lawns worse than that - in fact I'm doing one at the moment - when we moved here the last owner had ruined it by alternately neglecting then scalping it, and then we had three builders' skips on it for 6 months.
As Tootles says, rake vigorously with a spring tine rake, aerate with a garden fork (mind your toes - my brother stuck the fork right through his foot when he tried, but he was only 4 - we started gardening early) and sprinkle some seed on the bare patches - now is a good time - don't cover it with soil or anything, but water it in well.
Mow the lawn regularly, at least once a week. In warm weather following rain it will grow quickly and may need mowing twice a week. Don't mow it too short - scalping it is what results in the lumps and bumps and bare patches, and as Tootles has said, treat it gently this year - try to keep off the re-seeded patches. And keep your mower blade sharp or replace it so that it cuts rather than chews the grass.
It'll look a lot better by the end of this summer and next summer you'll have a lawn to be proud of.