What type of paint did you use ? It is difficult to blend metallic paint which is why some times the whole panel requires painting . In this case , it looks like you sanded too far into or thru the new paint .
The only way I've had acceptable luck blending into a small area is w/ a single stage urethane paint or w/ lacquer.which is hard to get nowdays & must be applied in very light coats . You may be able to rectify what you have by airbrushing on another coat of base & clear , sand LIGHTLY , then buff or hand rub w/ a medium rubbing compound . I've recently used paint & primer to do small jobs from Microfinish ,New Orleans , which they supplied in aerosol cans to match my wife's Camry & was surprised at the match & quality ! For about $60 I got a can of good quality primer , paint (I think urethane) , & a can of topcoat for less than the price of a pint of urethane at a paint shop .
Their ph is 888 710 5192 .
Good luck !