It may still be useful, but the exact handling depends on the firm's recruiting system and where your application is in the process.

A referral submitted after the application can sometimes be connected to an existing candidate record, but you should not assume it happens automatically. The recruiter may already be reviewing the application or the system may have specific referral timing rules.

If the consultant receives confirmation that the referral was submitted, you can keep that record and, if appropriate, ask recruiting whether the referral is visible on your existing application rather than submitting a duplicate application.

Do not create a second application. Confirm with the referrer that the referral was submitted, then contact recruiting only if needed to check whether it has been attached to your current application. If useful, this guide on consulting referrals gives more detail.

Mine went in after I applied and recruiting could still see it, but I had to check.

Definitely don't submit another application just because of the referral.