I had booked a ticket for travel through Indian Railways using IRCTC and got a confirmed ticket. While booking, I forgot to mention the details of a one year old child who will also be traveling.
Will it create any problem while boarding the train?
Traveling with less than 5 years child with out mentioning their details in the ticket in Indian Railways is not a problem.
In your case for a one year child, the Train Ticket Examiner (TTE) won't ask any details. In my experience, you can tell the truth to TTE they won't make any issue.
The ticket fare applicable for more than 5 years old children only.
The other answer is perfectly correct, travelling with one or even more children of age 5 and below is not a problem, the reason I am adding another answer is just so that everyone visiting in future understand the full implications.
The details of Children travelling together with adults is taken for use in emergency alone. In case if there is an emergency and god forbid the child is left alone, this information is used to track them and hence in future please make sure this information is provided.