You will probably have to carry out lawn repairs - grass does not cope well with foot traffic when the weather's very cold - even sports turf has to be repaired and nurtured all the time. You can either wait and see if it recovers, or take action now or as soon as weather allows - either by returfing or scraping up the bald areas to give a depth of friable soil to a couple of inches, sow seed. Note that new seeded grass cannot be used normally, and specially not for football, for 3 months.