You can try dissolving your nitrile in DMSO (0.3 mL/mmol), cooling to 0 ºC, and adding H2O2 30% (0.12 mL/mmol) and anhydrous K2CO3 (20 mg/mmol). Allow the mixture to warm up to r.t. In no more than 30-60 minutes your amide should be formed without hydrolize your ester group in good yield (I hope...). Add water to the mixture and purificate if necesary.