Not eating when poorly

My baby is nearly 11 months old and seems to have quite a bad cold. He went to nursery for a settling in hour a couple days last week for his start in Jan and played with the one kid that was poorly🫣😂 he is now full of a snotty cold. He isn’t his usual self he clearly feels sorry for himself but generally he is pretty happy through the day. Only thing is he’s hardly eating. He will take milk which I am happy about but before being poorly he was always food over milk he shouldn’t ever stop eating but hardly finished a bottle. Now he won’t touch much food and only wants milk. When should I be concerned? As he is pretty happy I’ve not stressed too much but I don’t want to make him more unwell letting him refuse food. He’s had lots of medicine and rest but it’s been a week and doesn’t seem much better