I'm 4 weeks post op. One butt implant harder than the other?

What you say sounds completely normal. The two buttock cheeks are different units and a totally symmetric healing  would anti-natural. Imagine you had fractures on both of your legs: healing will be speedier on one side than on the other, one side will swell more than the other so such a short time after surgery nothing to worry about.The earliest that I would start to be concerned would be three months after the procedure, and no action is usually considered before 6 months have past.So no worries for now, enjoy your results !

Dear Ingrid,  Front and side view pictures would have been helpful. You are very early in the healing process and it might take 3-4 months for the butt to soften up. I would recommend to perform 3 times daily, 3 repetition of implant displacement massage, to loosen up the pocket, which will soften the butt.   If after that period things do not improve, you might want to discuss with your surgeon you condition and consider the need for capsulotomy (scar release) , which will enlarge the pocket and soften the butt.    If you have significant fluid build up in the pocket and the capsule is inflamed (can be seen during the above mentioned procedure), you might have 'Biofilm' that requires cauterization of the capsule and replacement of the implant.    I hope this is helpful to you,                                    Best of luck,                                                    Dr Widder

You may have some capsular contracture. its important to keep your regular follow up appointments with your surgeon and follow post op instructions closely.