This is a VERY common thread on this forum and a search of other responses would be very helpful to you. Click on:
https://forum.freeadvice.com/search.php
Simply, yes, you can pursue litigation, but your chances of success will hinge on the following:
1) Do you have any proof that the funds were loans and repayment terms? If not, it is your word against his (I am sure he will claim that they were gifts). Judge Judy has cases like this all the time and a large part will be your ability to show/prove them as loans.
2) Where does he live in relation to you?? Where were the funds paid and where was the agreement entered?? These are all questions that could affect the venue of the applicable court(s).
3) Your full amount ($7,000) exceeds the jurisdictional limit of most Small Claims actions. You will need to decide if you will settle for less and save attorney costs, or go for all of it which will require filing in a higher court.
4) Finally, you need to be aware of the Statute of Limitations. Ohio is FOUR years, so you are getting VERY close to losing all rights of recovery.