Yes. If you're a free developer (you have to register as a developer to even do this), you have to re-authorise the app every 7 days or it gets "revoked" which means the app will not launch.
You also have to install a certificate that certifies the app(s) to you. This is generally safe, but you should be careful with trust certificates. You're basically taking full responsibility for the code that's being executed on your device. If you haven't audited the source code (or if someone you trust hasn't), it might be a risk.
If you used a signing service, someone has bought a bunch of paid developer licenses and they've given you the certificate for one of them. Once Apple discovers this, they'll revoke that developer license which revokes your apps. The signing service will then issue you a new certificate. Revokes aren't super common, or so they say (I've never used a signing service).