Does a legal limit exist for filing a report of police misconduct, w/the internal affairs unit where the officers are stationed?

There is likely a separate Internal Affairs Unit

If you sustained injuries due to police misconduct, a civil rights lawyer can investigate a civil claim against them.

Our office regularly handles civil Rights claims, as do many others on this site... Generally, you have to file a notice of claim within 90 days of the incident happening. If this deadline has expired there is some potential to file up to a year and 90 days through a motion with the court, the judge would have to grant permission. Finally, if you've not met this deadline then you have the ability to file a claim in federal court up to 3 years from the date of the incident (or the date of the dismissal for malicious prosecution claims). I would suggest contacting an attorney as soon as possible and getting things started immediately so as to avoid missing any of the deadlines above.