[Grammar] came to know/ knew

[butwas]

My friend was planning to have a birthday party but for various reasons he had to cancel it. And if am to know that on his birthday, which of the following is correct ?
1.Today only i knew you ain't celebrating your birthday.
2.Today only i came to know you ain't celebrating your birthday.

Now, in case both are grammatically correct please comment on how a native speaker is likely to say it.

 

[bhaisahab]

My friend was planning to have a birthday party but for various reasons he had to cancel it. And if am to know that on his birthday, which of the following is correct ?
1.Today only i knew you ain't celebrating your birthday.
2.Today only i came to know you ain't celebrating your birthday.

Now, in case both are grammatically correct please comment on how a native speaker is likely to say it.

Nieither one is correct. Try "I only discovered today that you had cancelled your birthday party".

Please give correct information in your profile.

 

[Raymott]

1.Today only i knew you ain't celebrating your birthday.

"Ain't" is substandard in most places.