Maintaining Credibility with Data Obtained by Hand
There is probably little to do but be honest about how the data was obtained. If it holds up under review then you have no issues. The past is the past. 

However, if you have a chance you can try to obtain a better data set under more controlled conditions. This might be the core of a follow-up publication, either validating or invalidating the earlier result. 

You learn something from just about every study. But if you are honest, it is hard to complain.