I wouldn’t look too far into “lack of experience”. It sounds to me like a pretty generic cop out reason to give to a recent grad - what ever the actual reason may have been.
Overnight, there’s nothing you can do to suddenly have more experience. Just make sure that in person you’re not coming off as immature. Maybe have a pretend interview with someone you know (preferably someone with hiring experience or at least a decent amount of work experience) and see if they notice anything blatant in your interview style.
With that said, I would polish your portfolio. I would also suggest against focusing on freelance work. The projects you’re likely to reel in won’t be very relatable to the kind of work you ultimately want to get hired for. I’d look for an internship and spend a lot of time redoing your portfolio and adding more projects. Even better if you can find collaborators for your projects.