ERROR ITMS-90725: "SDK Version Issue. This app was built with the iOS '10.3' SDK. All new iOS apps submitted to the App Store must be built with the iOS '11.0' SDK or later, included in Xcode [9.0] or later. Please update Xcode and rebuild your app."
getting this error. Is there any way to upload app without updating the xcode?
No. You need to get a newer version of Xcode. This may involve in you having to fix your code so it's building correctly on a newer Xcode. There may be hacks to get the iOS 11 SDK into Xcode 7.3 but you're very likely to spend a lot of time with this and still fail.