I'm a new duckling mommy

Hi everyone. My mom gifted us a baby duckling. IDK anything about him/her other than its tiny. Still a baby. We have a small cage where he sleeps and he has duckling food and fresh water all the time. We are all gentle with him. We let him out to walk the backyard for a little bit while i am there or one of the older kids is. We also let him play with us in the house for a while at times. He is a pet. Ive had him a few days and already he has won my heart. I am writing because just a while ago I noticed one of his little feet is bruised. No cuts and hes eating and drinking well. He limps but very little. I made a small water bath for him and he bathed and splashed till he tired then I put him in his cage while he did his usual grooming. He is eating now and settling to sleep ( his normal routine). What can i do to help his foot? its bruised but not broken or bleedin. I will keep him in his cage until he heals and just take him out for baths. We only use cool water. our house is warm and we cover his cage at night also.
This is just until he is big enough to sleep in a coop outside ( in the summer). Does he need to see a vet? I plan to take him to a vet later for checkups. What advice do you all have for me? BTW thanks for this awesome forum!

@powrpuff Welcome to BYC and Congrats on your new duckling.
I want to give you some great info on caring for your duckling. https://www.backyardchickens.com/t/750869/raising-and-caring-for-ducklings#post_10611711

Now to the foot, could his/her foot gotten stepped on by accident? It looks pretty bruised and they can get under foot pretty quick. I'd just keep an eye on it as long as nothing feels or looks broken. You can also soak the foot in some warm Epsom salt water I'd use a cup for the lil one and make sure he doesn't drink out of it [Epsom salt is also a laxative] but great for swelling and bruising. Half teas to 1 cup of warm water. and please if your letting the little on swim make sure the water is warm when they are only in down they have no way to control their body temp and can chill very easy. They also need to be kept at temps from hatch at around 85* then drop that temp 5* each week there after till same as house temp. This info will be your best guide to keeping your duckling healthy and happy.