Congratulations!!! Walmart is a good card to have!!! It will grow!! It won't hurt to apply for another store card if you want. That way the inquiries can age and fall off around the same time!!! I applied for Walmart, Amazon and Care Credit last year all at the same time and got approved! Now I'm letting them age and grow and won't apply for another card until I get my new house and apply for Lowe's! Once again! Congrats OP!
Congrats on the approval!
Congrats and like others have mentioned, you should to get try for a rewards prime card like Citi Double Cash or QuickSliver if your at 630 score on actually FICO (NOT CREDIT KARMA SCORES).