Injured robin

Hello I have a very friendly robin that has followed me round the garden wherever i go.  He would feed from my hand  and come into the greenhouse to spend time with me,  a Cple of weeks ago he couldn't get enough food from me, he would fly away with it in his beak  ,obviously feeding his family,   a week ago I noticed how bedraggled he was ,and his beak was permanently open.  He now has a rival robin coming in garden attacking him. How can I help him and how can I get his beak to close again,   I am breaking his suet pellets to very small pieces  and also watering plants so he can drink from the leaves,

Any guidance would be really appreciated please,  

Anne