The only option would be to try to reopen the case based on an ineffective assistance of counsel claim, but that is a steep, steep hill in most cases and likely insurmountable in yours. The elements are:
1). Counsel's performance was not just a matter of quality, but that Counsel's representation of the Defendant was so seriously deficient that Counsel was not acting as a Counsel, and his action(s) or lack thereof, denied the defendant his Sixth Amendment Right (guarantee) to Counsel.
2). Counsel's performance, or lack thereof, prejudiced the defense so as to deprive the defendant(s) of a fair trial, and the verdict and/or result(s) that a fair trial would have rendered.
The problem is that you entered a plea. At the time of the plea you were instructed by the court about your rights and asked if you understood them. That colloquy will be recorded in the audio transcript of the hearing. Because of this, there is a 99.99% chance that any challenge would be fruitless.
Unfortunately, what you have been previously advised is also true and that this event can't be sealed or expunged.
The only other option would be a pardon. This will not erase your record, but the pardon will appear next to the charge.
Please let me know, if you have follow-up questions.
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