If I paid son's tuition, but did not get a 1098-T, can I still claim it?

It depends. You can claim qualified education expenses if your son was your dependent.

The school has to issue a 1098-T for you to claim expenses. You didn't say why you didn't a 1098-T. If it was never sent or sent to your son, you can claim the expense. You can't claim it if the school or program was not qualified. For example, it was located overseas or a nonqualifying trade school.

The IRS has an interactive assistant to help you decide whether you can claim a credit: Am I Eligible to Claim an Education Credit?

Most schools have an online portal where students download the 1098-T. 

If this is a divorce situation and the other parent is claiming the student as a dependent, then that parent is the only one who can claim the tuition credit. They may count the tuition, paid by you, when calculating the credit for themselves.