Your blank solvent is contaminated, perhaps you took the blank sample from a blank solution that you already used to prepare your samples. Always use fresh blank to vial before you prep samples. Other causes may be carryover from the needle, maybe your needle wash needs to be changed. Normally I would inject blanks first, then a std, then the blank again and you will be able to tell if there is carryover from the previous injection. This can be a problem throughout your run if you are adding carryover from the previous samples your results won't be accurate.
If it is your column, maybe your runtime isnt long enough, does your peak return to baseline for long enough before the next injection? Anyway it sounds to me like your column is not the problem.