If you use a technology design that has a non-expired patent application, once that application has been approved, assuming it will, then will the product be considered a patent infringement? Are there any issues to address now that the patent has been approved? What to do and what to fix?
What you are asking about is called provisional rights. Not be confused with the completely unrelated "provisional patent application".
If a person infringes the invention claimed in a published patent application, and that application is later granted, the patent owner is entitled to a "reasonable royalty" from the infringer (35 USC § 154(d)(1)), if:
the infringer had actual notice of the publication (35 USC § 154(d)(1)(B)); and
the invention claimed in the patent is substantially identical to the patent claimed in the published patent application (35 USC § 154(d)(2)).
What to do now that the patent has been issued?
Well first, stop infringing the patent. Then get yourself a lawyer to assess your liability for infringing the provisional rights.