If your child does not have a fever, it is at least a good sign and does not require immediate medical attention. Being tired can be normal; his body is working to produce antibodies to fight the infection, so it's taking a lot of his energy. At this time, make sure your child is well hydrated and rested. If your child has a cold or viral infection of any kind, the bulk of the symptoms will occur in the first 2-3 days and will get better after 7-10 days in total. If these symptoms worsen or go beyond this period, a medical consultation would otherwise be in order.
I hope this answers your question. If you have any other concerns or have more pertinent information to pass on, please do not hesitate to contact me again and I will be happy to answer.